Electrode surfaces have been coated with various polymeric materials for a variety of purposes. For example, in various applications, it has been desirable to coat electrode surfaces with polymeric materials that allow for the transmission of electric charges on the electrode surface. A process that is frequently used to coat an electrode surface with a conductive polymeric material involves the production, propagation, and combination of radical precursors to form the desired polymeric coating, such as a polyvinyl coating, on the electrode surface.
In certain applications, it is desirable to confine the transmission of electric charges to specific portions of the electrode surface. However, as electrodes have become smaller and smaller with advances in technology, it has become difficult to control the coating of the electrode surface to confine charge transmission on the electrode surface precisely enough for certain applications. For example, some electrodes of reduced size cannot be manufactured because it is not currently possible to coat the electrode surface precisely enough to prevent the entire electrode surface from becoming electroactive. Any improvement in the modification of electrode surfaces, and particularly, microelectrode surfaces, is therefore of considerable interest.
Polymer-coated electrodes may be used as electrochemical biosensors. For example, in a glucose biosensor, a working electrode coated with a redox polymer film that electrically connects or “wires” reaction centers of an enzyme, such as glucose oxidase, to the electrode, can be used to glucose that is electrocatalytically oxidized by the “wired” enzyme at the electrode surface. See, for example, A. Heller et al., U.S. Pat. No. 6,251,260. There is an increasing interest in miniaturizing biosensors, such as the glucose biosensor just described, particularly in the development of implantable biosensors.
Polymer-coated electrodes may also be used in the sensing of chemical and biological molecules, such as DNA-containing molecules. By way of example, an electrochemical system employing an electrode that is coated with a redox polymer film, in which sensor molecules and enzymes are immobilized, has been developed for use in affinity assays, such as sandwich-type immunoassays, for the detection of various biological ligands. See A. Heller et al., U.S. Pat. No. 6,281,006. Further by way of example, a multi-sensor array of electrodes, coated with a redox polymer film and nucleic acid sensor molecules, has been developed for the electrochemical recognition of nucleotide sequences. See De Lumley-Woodyear et al., U.S. patent application Publication No. 2002/0081588. The above-described redox polymer coatings may be electrodeposited on the electrodes. There is a keen interest in the refinement or further development of such sensors for chemical and biological assays, including the development of electrodeposition processes used to produce the sensors.
Many of the electrochemical biosensors marketed today, such as the glucose sensors used by diabetics to monitor blood glucose levels, are based on screen-printed carbon electrodes that are mass-produced at low cost. The development of electrodes with useful surface coatings, such as those suitable for glucose sensing, or for various chemical or biological assays, that can be mass-produced is of considerable interest. The development of means for electrodepositing useful coatings, such as thin, redox polymer films, on electrode surfaces, and particularly, on a mass-production basis, is similarly of interest.